In the past a variety of different types of devices have been developed to drive fasteners into a substrate for various purposes. The type of device most often utilized to drive the fastener is a screwdriver or similar device that translates the rotation of the screwdriver by the individual into rotation of the fastener to urge the fastener into the desired substrate.
On many occasions, the particular location where the fastener needs to be located, or the type of substrate into which the fastener is to be driven creates a certain amount of difficulty in driving the fastener into the substrate. To provide some assistance in driving the fasteners in these more difficult situations, many of these devices are constructed with a ratcheting mechanism. The ratcheting mechanism allows the individual to restrict the rotation of the driver to a single direction, which eases the difficulty of driving the fastener.
Nevertheless, the devices, whether including a ratcheting mechanism or not, produces only a one to one ratio between the rotation of the device by the individual and the corresponding rotation of the fastener. As a result, it normally takes a significant amount of time to completely drive the fastener into the substrate.
In an attempt to increase the speed of driving a fastener into a substrate, certain prior art devices have been developed that can alter the ratio of the rotation of the handle of the device with respect to the driving bit of the device, to thereby increase the speed of driving the fastener into the substrate. One device of this type is disclosed in Murphy U.S. Pat. No. 6,899,653, which discloses a fastener with a gear assembly. In this device, the fastener includes a plate having a number of openings formed therein. The plate is connected to a sun gear which engages a number of planetary gears positioned between the sun gear and a ring gear disposed on the exterior of the device. When engaged with and allowed to rotate freely with the planetary gears and the ring gear, the sun gear rotates at a speed faster than the rotation of the handle, at a ratio of approximately four rotations of the sun gear for each revolution of the handle. Further because the driving bit for the device is fixed to the sun gear, the bit also rotates at the 4:1 ratio to drive the fastener engaged with the bit into the substrate at a speed greater than the rotation of the device handle by the individual.
The device also includes a switch located on the exterior of the device, and that is slidably movable with respect to the device. The switch includes a pin that can be selectively engaged and disengaged with one of the openings in the plate to which the sun gear is attached. Thus, when the pin is engaged with the plate, the pin prevents the plate and the sun gear from rotating separately from one another, so that the sun gear, as well as the bit connected thereto, and the handle rotate in a 1:1 ratio.
However, while providing a design that enables the device to be operated at different gear ratios to increase the speed of the driving bit as desired, the device requires a separate switching mechanism to transition the device between the different gear ratios. This requires a additional and separate mechanism to be formed on the device, which significantly complicates the construction and operation of the device. In addition, the switching mechanism relies solely on the frictional engagement of the pin with the plate to maintain the lock between the plate and the pin, such that the switching mechanism can be inadvertently disengaged in a relatively easy manner. Also, the switching mechanism requires the alignment of the pin with an associated opening in the plate in order to engage the switching mechanism, which often requires that the device to be moved from a desired position in order to align the pieces of the switching mechanism.
Accordingly, the prior art does not satisfy the needs and solutions required for devices of this type, such that it is desirable to develop a fastener-driving device that provides a simple construction and mechanism for altering the speed of rotation of the driving shaft relative to the handle.